Smart buildings are run by Cyber-Physical Systems (CPS), termed as Building Management Systems (BMS). Typical goals for the operation of BMS are increasing occupant comfort and decreasing buildings energy consumption. The central and critical figure, however, for achieving both goals are buildings' occupants. In some BMS, occupants have a high level of interaction with the system, whereas in others this is limited to a large extent, barring occupants from even opening windows. Every interaction, however, is a form of feedback, which in some cases poses a risk, whereas in others, it is an opportunity to discover issues in the system. In this paper we aim to emphasize the complexity of buildings' occupants' behaviour and interactions with BMS. We further aim to identify the risks and opportunities that these interactions pose with respect to the circumstances that lead to them and their impact towards achieving BMS' goals. We, furthermore, provide classification of occupant interactions based on their circumstances and relate this to their meanings with respect to BMS goals.